1. Jethro says

    Reading the source page, it appears that the hectocotylus is the severed third left arm of a male Argonaut. Presumably the torn looking part in the middle is where it used to be attached to the male.

  2. David Marjanović says

    The thick end is attached to the rest of the male. The thin end goes into the female.

  3. bodach says

    Thanks for the clarification, Jethro; I went to the link and saw a lot of sciencey words and had to go back to work.